Flash evaporator



Allg- 1965 w. cs. KINGMA 3,203,464

FLASH EVAPORATOR Filed Nov. 13, 1962 INVENTOR W0 UT ER' 6. K\NGMA ATTORNEYS United States Patent 3,203,464 FLASH EVAPORATOR Wouter Gerhard Kingma, Nuizen, Netherlands, assignor to Werkspoor N.V., Amsterdam, Netherlands, a Dutch company Filed Nov. 13, 1962, Ser. No. 236,919 Claims priority, application Netherlands, Nov. 17, 1961, 271,501 Claims. (Cl. 159-2) The invention relates to a flash evaporator provided with a number of flash chambers arranged horizontally downstream of each other, each chamber being connected near its bottom to the adjacent chamber and in each of the chambers reigning such a pressure that the absolute pressure in the evaporator decreases in the direction of the liquid outlet.

The invention has for its object to improve an evaporat-or of this type in such a way that the evaporator can operate with a relatively small liquid content and with relatively large specific loads.

According to the invention the connecting channel between one chamber and the next one is constituted by a plate extending horizontally at some distance above the common bottom of the chambers, said plate at the end reaching into the adjacent downstream chamber being prolonged by an upwardly inclined part. With said arrangement vapor is generated in the channel formed by said plate, so that the volume of the liquid is increased and the mixture of liquid and vapor flows out the channel into the adjacent chamber with a large velocity. As at its outlet the channel is widened by the upwardly inclined part of .the plate the mixture gradually expands and the liquid is split up in large drops whereby the liquid presents a large surface area. Therefore, flashing occurs at small pressure drops between successive chambers so that the evaporator may operate with large specific loads.

The invention will further be described with reference to the accompanying drawing showing an embodiment of the evaporator according to the invention, and in which:

FIG. 1 is a longitudinal section through a number of flash chambers of an evaporator;

FIG. 2 is a sectional view on a larger scale through the connecting channel between two chambers;

FIG. 3 is a view corresponding with FIG. 2 in another embodiment of the connecting channel, and

FIG. 4 is a sectional view taken on line 44 of FIG. 1.

The chambers arranged downstream of each other have a common plane bottom 1. The chambers are formed by partitions 2. Each partition 2 joins with a horizontal plate 3 which leaves a slot like channel 4 with reference to the bottom. At the entrance and exit of this channel the plate 3 has an upwardly inclined part 5 and 6 respectively, so that the downstream part of the channel has the form of a diffusor. At the bottom of the channel has been provided a transverse projection 7, (2.5;. in the form of a low threshold or of a round bar.

The upper regions of the chambers are crossed by horizontal pipes 9 which carry cooling water and form the condensors separated from the chambers by a wall 10, but connected with each other by overflow pipes 11 for the condensate. The non-condensable gases are exhausted at 14. From the last condensor the condensate is carried off by duct 13. The pipes 9 extend through holes in the partitions 2.

In each chamber, between the plates 3 but on a slightly higher level, is mounted a downwardly inclined guide plate 8, which receives the spray leaving the channel 4 and guides the liquid to the entrance of the next channel 4. The guide plate 8 prevents that the spray leaving the ice channel 4 will contact the vertical partition 2, which would cause the forming of a mist. The vapour which is substantially free of mist can flow at both ends of the guiding plate 8, through the passages left by the guiding plate with respect to the plates 3, to the condensor via an opening 12. The openings 12 are provided in a longitudinal wall of a casing enclosing the bank of pipes 9 and having its bottom constituted by the wall 10, as shown in FIG. 4. Because this opening 12 lies immediately downstream the vertical partition 2 the ascending vapour has to change its direction, so that the separation of liquid from the vapour is promoted. To this effect also a dropcollector can be arranged below the opening 12.

Owing to the above mentioned factors a large vapour velocity and a large water load is allowable, so that the evaporator according to the invention can be small and cheap.

By a suitable choice of the length L of the slot like channel and the height s of the channel vapour is prevented from flowing through the channel from one chamber to the next although vapor generated within the chan nel does so flow. In a temperature region of 50 C. and with a temperature dilference of 1.5" C. very good results were obtained with a ratio L/s=4. The projection 7 had a height of 2 cm. and had been situated in the middle of the channel. The load was 400 tons salt water per hour and per meter of the width of the chambers and without using a drop collector, a concentration of 0.5 milligram chlorine per liter in the condensate was measured. The liquid level in the chambers rose very little due to damming up in the channels. The capacity of the evaporator could be varied while maintaining the low liquid filing of the chambers.

As shown in FIG. 3 the channel 4 can have the form of a venturi. This form is very advantageous in the case of large temperature differences of 5 to 10 C. between the chambers.

The bottom 1 of the chambers can also have a very slight slope.

The described evaporator is not only suited for water like liquids but also for more viscous liquids, e.g. for preparing the feeding in catalytic cracking processes in the oil-industry and for the evaporation of strongly foaming solutions, e.g. coagulating liquids, because eventually formed foam is destroyed by the spray of large drops. Due to the spraying of the foam the concentration of surface active agents, in the foam remains low, so that the foam is mechanically less strong. The flash chambers can be much smaller than in the normal circulationor flowthrough evaporators with external vapour separator.

What I claim is:

1. A flash evaporator comprising a plurality of flash chambers arranged substantially horizontally downstream of each other on a common bottom, each said chamber being connected near its bottom with the adjacent chamber by a channel so constructed and arranged that the absolute pressure in the evaporator decreases in the downstream direction, each said connecting channel having one wall formed by said common bottom of the cham- Hers and a second wall formed by an imperforate plate spaced above the common bottom and extending horizontally from the interior of one chamber into the interior of the adjacent chamber, and each of said plates at the end reaching into the adjacent downstream chamber being prolonged by an upwardly inclined part forming a downstream-facing dihedral .angle with said common bottom.

2. A flash evaporator as claimed in claim 1 wherein each of said plates at its end reaching into the adjacent upstream chamber is also prolonged by an upwardly inclined part forming an upstream-facing dihedral angle with said common bottom.

3. A flash evaporator as claimed in claim 1 wherein a transverse, vertically directed, turbulence causing projection is provided at the bottom of each connecting channel.

4. A flash evaporator as claimed in claim 1 wherein a substantially horizontal guide plate is arranged in each chamber, said guide plates being spaced from the ends of said plates forming part of the connecting channels between chambers to leave passages for vapor to move up- 10 wardly.

5. A flash evaporator according .to claim 4 wherein each of said guide plates is slightly inclined downwardly in the downstream direction.

References Cited by the Examiner UNITED STATES PATENTS 445,266 1/91 Rodgers 15932 2,168,875 8/39 Noll.

2,446,997 8/48 Brewster 202205 X 2,944,599 7/60 Frankel 15917 X FOREIGN PATENTS 1,090,178 10/60 Germany.

831,478 3/60 Great Britain.

855,550 12/60 Great Britain.

NORMAN YUDKOFF, Primary Examiner. 

1. A FLASH EVAPORATOR COMPRISING A PLURALITY OF FLASH CHAMBERS ARRANGED SUBSTANTIALLY HORIZONTALLY DOWNSTREAM OF EACH OTHER ON A COMMON BOTTOM, EACH SAID CHAMBER BEING CONNECTED NEAR ITS BOTTOM WITH THE ADJACENT CHAMBER BY A CHANNEL SO CONSTRUCTED AND ARRANGED THAT THE ABSOLUTE PRESSURE IN THE EVAPORATOR DECREASES IN THE DOWNSTREAM DIRECTION, EACH SAID CONNECTING CHANNEL HAVING ONE WALL FORMED BY SAID COMMON BOTTOM OF THE CHAM- 